There comes a time in any car's buildup when you're no longer happy with bolt-ons. Although the less expensive modifications have proven to be beneficial to performance, the brick wall is finally in your face, and the next leap is a big one. Some prefer to steer away from such a move, but for those of us who can't settle for good, the next frontier generally means getting into the engine. For us, good becomes gooder with a new cylinder head and intake package.
When most people think of cylinder heads, they're often daunted by the huge variety of offerings for the small-block Chevy. Although it seems like a good thing at first, research will soon reveal there aren't as many options for LT1 enthusiasts because there simply aren't as many heads on the market. Many companies skipped the LT1 market and went straight for the LSX scene, but now that LT1 engines are in great abundance, several companies are now refocusing attention to the Gen II small-block introduced in 1992.
Edelbrock-which has been on an absolute tear recently with all sorts of new cylinder heads for various American V-8 applications (both popular and obscure)-recently released a line of aluminum heads for both the LT1 and high-port LT4 engines. Yes, following along in its Performer RPM line of heads, these new castings promise Gen II owners something to look forward to with respect to performance, value, and weight savings. The best part about it is that Edelbrock sells them either bare for the hardcore engine builders or as a complete assembly for guys like us who like to bolt-on and go.
Headin' OutEdelbrock's Performer LT1 aluminum cylinder heads feature many goodies that you'd expect, including generous 2.02/1.55 valves, CNC port-matched runners, and high-lift valvesprings for use with hydraulic roller camshafts. Unlike some other heads on the market, Edelbrock goes a step further and uses steel thread inserts on all the attachment points for more secure fastening. If any of you out there have ever stripped a thread in an aluminum cylinder head, then you can really appreciate this attribute.
Also, Edelbrock's heads bolt right on without the use of any special-length fasteners or exotic valvetrain components. This keeps costs down as you take the plunge into the top-half world of more power. Available bare or complete, they're sold separately, and we went with the ready-to-run units listed under part number 61909. To install them, we picked up a set of new GM head bolts procured from the local Chevy dealer to do away with the factory torque-to-yield bolts.
To complement the heads, we decided to ditch the factory intake manifold and go with Edelbrock's matching Performer LT1 intake manifold. Aside from offering larger ports that properly match up to its heads, Edelbrock's manifold also has larger openings on the throttle body side that can accommodate 58mm throttle bores. Although our car is only equipped with a 52mm twin-bore unit (stock is 48mm), it's good to know that should we choose to upgrade in the future, the option is there for us.
It's interesting to note that a version for LT4s is also available that includes the taller port location. Edelbrock also offers LT4 cylinder heads for those who want to go beyond their '96 C4's 330hp rating.
Rounding out the installation is a set of hardened 7.3-inch pushrods and self-aligning roller rockers from Comp Cams. With its roller bearing mount and lightweight aluminum construction, the 1.5 roller rockers (part number 1015-16 for the set) will help us pick up some incremental power from reduced parasitic friction on the top half. It should be noted that it's not necessary to replace them when using the Edelbrock heads, so if you wanted to, you could reuse the stock rockers.
We left the stock camshaft in place. It has a torque-oriented profile for the iron-headed LT1, with its 260-horsepower rating. This cam checks in with an advertised duration of 205/207 degrees, and total lift with the 1.5 rockers is .447/.459 for the intake and exhaust, respectively. LSA is at 117 degrees, and compared to earlier '94-95 LT1s, our cam specs are milder on our '96, no doubt a concession to OBD-II. We'll stick with it for now to see how the intake and heads work out by themselves. We'll address this cam situation later.
Looking for an LT1 expert to install our new top half wasn't as easy as it used to be. Quite frankly, everyone is now involved with LSX cars, so finding a good shop is no longer a walk through the small-block park. However, experienced LT1 technicians can still be found within the veteran ranks of the GM performance movement, so we were happy to find John Moundros of J&T Auto in Huntington Station, New York, in our Rolodex.
Once there, we quickly got to work as Tom O'Sullivan (aka "Big Tom") started turning the wrenches while we shot the pictures. After a full day of work, we finished the installation and promptly took our cop car back to Raceway Park in Old Bridge Township, New Jersey. Once there, we quickly cooled our car down, slapped on the Nitto Drag radials, and went for broke. With the car staged shallow and stalled on the converter, we mashed the gas and were rewarded with an incredible 13.903 at 96.55 mph on the first pass. This represents a drop of five-tenths (.501, to be exact) and a gain of 3.74 mph from our previous best of 14.405 at 92.81 mph.
Excited and very satisfied with our all-motor performance, we then armed the Zex nitrous system and made another run. This time around, we launched at the same rpm and left with a 1.76 short time and dropped our e.t. to an incredible 12.855 at 101.44 mph. Previously, our best time with the stock heads and intake manifold with the nitrous armed was 13.522 at 98.70 mph, so our gains were substantial, but the car hit the rev limiter at about 1,200 feet out and rolled through the traps. With the 27.76-inch tire height of the 275-60-15 Nitto drag radials and the 3.73 gears, we should have had enough room to make a full pass, but with the higher-stall torque converter and the relatively low 5,400-rpm limit of the factory PCM, we just couldn't go any faster. It's too darn bad, because we felt there was at least another .020 in e.t. and 1 mph in it.
Now that we're staring at a stack of wrinkly old timeslips, it's time to start optimizing our setup. In our next installment, we'll look at some other internal engine mods and try to unlock some hidden potential in that aluminum-cased brainbox sitting in the engine compartment. Long live the Cop-rice!
The rocker's arms are then adjusted. We like to tackle this by making sure we adjust the valves while the lifter is on the lobe's backside. To do this, rotate the engine until the cylinder you're working on is about to open its exhaust valve. Now, adjust the exhaust valve. After pushrod contact, turn the adjuster about one-half to three-quarters of a turn and lock down the polylock.
With the engine assembly complete, it was time to fill the engine up with fresh fluids. Here, "Big Tom" uses an incredibly fancy filling system that purges all traces of air important, because any air pocket in the system will cause teh car to overheat, damaging the engine, and in a worst-case scenario cracking hard parts.